Exposure-response analyses of erdafitinib in patients with locally advanced or metastatic urothelial carcinoma

Background

Exposure–response analyses were conducted to explore the relationship between selected efficacy and safety endpoints and serum phosphate (PO4) concentrations, a potential biomarker of efficacy and safety, in locally advanced or metastatic urothelial carcinoma patients with FGFR alterations treated with erdafitinib.

Methods

Data from two dosing regimens of erdafitinib in a phase 2 study (NCT02365597), 6 and 8-mg/day with provision for pharmacodynamically guided titration per serum PO4 levels, were analyzed using Cox proportional hazard or logistic regression models. Efficacy endpoints were overall survival (OS), progression-free survival (PFS), and objective response rate (ORR). Safety endpoints were adverse events typical for FGFR inhibitors.

Results

Exposure-efficacy analyses on 156 patients (6-mg = 68; 8-mg = 88) showed that patients with higher serum PO4 levels within the first 6 weeks showed better OS (hazard ratio 0.57 [95% CI 0.46–0.72] per mg/dL of PO4; p = 0.01), PFS (hazard ratio 0.80 [0.67–0.94] per mg/dL of PO4; p = 0.01), and ORR (odds ratio 1.38 [1.02–1.86] per mg/dL of PO4; p = 0.04). Exposure-safety analyses on 177 patients (6-mg = 78; 8-mg = 99) showed that the incidence of selected adverse events associated with on-target off-tumor effects significantly rose with higher PO4.

Conclusions

The exploratory relationship between serum PO4 levels and efficacy/safety outcomes supported the use of pharmacodynamically guided dose titration to optimize erdafitinib’s therapeutic benefit/risk ratio.

Clinical trial registration number

NCT02365597.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00280-021-04381-4.

Erdafitinib's effect on serum phosphate justifies its pharmacodynamically guided dosing in patients with cancer

A population pharmacokinetic (PK)–pharmacodynamic (PD) model was developed using data from 345 patients with cancer. The population PK‐PD model evaluated the effect of erdafitinib total and free plasma concentrations on serum phosphate concentrations after once‐daily oral continuous (0.5–12 mg) and intermittent (10–12 mg for 7 days on/7 days off) dosing, and investigated the potential covariates affecting erdafitinib‐related changes in serum phosphate levels. Phosphate is used as a biomarker for erdafitinib's efficacy and safety: increases in serum phosphate were observed after dosing with erdafitinib, which were associated with fibroblast growth factor receptor target engagement via inhibition of renal fibroblast growth factor 23–mediated signaling. PK‐PD model‐based simulations were performed to assess the approved PD‐guided dosing algorithm of erdafitinib (8 mg once‐daily continuous dosing, with up‐titration to 9 mg based on phosphate levels [<5.5 mg/dl] and tolerability at 14–21 days of treatment). The serum phosphate concentrations increased after the first dose and reached near maximal level after 14 days of continuous treatment. Serum phosphate increased with erdafitinib free drug concentrations: doubling the free concentration resulted in a 1.8‐fold increase in drug‐related phosphate changes. Dose adjustment after at least 14 days of dosing was supported by achievement of >95% maximal serum phosphate concentration. The peak‐to‐trough fluctuation within a dosing interval was limited for serum phosphate concentrations (5.68–5.65 mg/dl on Day 14), supporting phosphate monitoring at any time relative to dosing. Baseline phosphate was higher in women, otherwise, none of the investigated covariate–parameter relationships were considered clinically relevant. Simulations suggest that the starting dose of 8‐mg with up‐titration to 9‐mg on Days 14–21 maximized the number of patients within the target serum phosphate concentrations (5.5–7 mg/dl) while limiting the number of treatment interruptions. The findings from the PK‐PD model provided a detailed understanding of the erdafitinib concentration‐related phosphate changes over time, which supports erdafitinib's dosing algorithm.

Targeted therapies for advanced bladder cancer: new strategies with FGFR inhibitors

Inhibitors of fibroblast growth factor receptor (FGFR) represent an outstanding treatment approach for selected patients with urothelial cancer (UC). These agents are changing the clinical approach to a subgroup of UC, the luminal-papillary subtype, characterized by FGFR mutations, fusions, or amplification. In this review, we provide an overview of the results of recent clinical trials on FGFR tyrosine kinase inhibitors (TKIs) currently in clinical development for the treatment of UC: erdafitinib, rogaratinib, infigratinib, and the monoclonal antibody vofatamab. The Food and Drug Administration recently granted accelerated approval to erdafitinib for patients with advanced UC with alterations of FGFR2 or FGFR3 after progression on platinum-based chemotherapy. We also look at future therapeutic options of combination regimens with immune-checkpoint inhibitors as strategies for improving the antitumor effects of this class of drug, and for preventing or delaying the development of resistance.

Phase II, randomized, placebo-controlled study of dovitinib in combination with fulvestrant in postmenopausal patients with HR+, HER2- breast cancer that had progressed during or after prior endocrine therapy

Background

Overexpression of fibroblast growth factor receptor 1 (FGFR1), found in ≤8% of hormone receptor–positive (HR⁺), human epidermal growth factor receptor 2–negative (HER2⁻) breast cancer cases, is correlated with decreased overall survival and resistance to endocrine therapy (ET). Dovitinib, a potent FGFR inhibitor, has demonstrated antitumor activity in heavily pretreated patients with FGFR pathway–amplified breast cancer.

Methods

In this randomized, placebo-controlled phase II trial, we evaluated whether the addition of dovitinib to fulvestrant would improve outcomes in postmenopausal patients with HR⁺, HER2⁻ advanced breast cancer that had progressed during or after prior ET. Patients were stratified by FGF pathway amplification and presence of visceral disease, and they were randomized 1:1 to receive fulvestrant plus dovitinib or placebo. The primary endpoint was progression-free survival (PFS).

Results

From 15 May 2012 to 26 November 2014, 97 patients from 36 centers were enrolled. The frequency of FGF pathway amplification was lower than anticipated, and the study was terminated early owing to slow accrual of patients with FGF pathway amplification. The median PFS (95% CI) was 5.5 (3.8–14.0) months vs 5.5 (3.5–10.7) months in the dovitinib vs placebo arms, respectively (HR, 0.68; did not meet predefined efficacy criteria). For the FGF pathway–amplified subgroup (n = 31), the median PFS (95% CI) was 10.9 (3.5–16.5) months vs 5.5 (3.5–16.4) months in the dovitinib vs placebo arms, respectively (HR, 0.64; met the predefined superiority criteria). Frequently reported adverse events in the dovitinib (diarrhea, nausea, vomiting, asthenia, and headache) and placebo (diarrhea, fatigue, nausea, and asthenia) arms were mostly low grade.

Conclusions

The safety profile of dovitinib plus fulvestrant was consistent with the known safety profile of single-agent dovitinib. Dovitinib in combination with fulvestrant showed promising clinical activity in the FGF pathway–amplified subgroup. However, the data reported herein should be interpreted with caution, given that fewer PFS events occurred in the FGF pathway–amplified patients than was expected and that an effect of dovitinib regardless of FGR pathway amplification status cannot be excluded, because the population was smaller than expected.

Trial registration

ClinicalTrials.gov identifier: NCT01528345. Registered 31 January 2012.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0807-8) contains supplementary material, which is available to authorized users.

Targeting FGFR with dovitinib (TKI258): preclinical and clinical data in breast cancer

PURPOSE

Fibroblast growth factor receptor 1 (FGFR1) and FGFR2 amplifications are observed in approximately 10% of breast cancers and are related to poor outcomes. We evaluated whether dovitinib (TKI258), an inhibitor of FGFR1, FGFR2, and FGFR3, presented antitumor activity in FGFR-amplified breast cancers.

EXPERIMENTAL DESIGN

Preclinical activity of dovitinib was evaluated in both breast cancer cell lines and an FGFR1-amplified xenograft model (HBCx2). Dovitinib was then evaluated in a phase II trial that included 4 groups of patients with human EGF receptor 2-negative metastatic breast cancer on the basis of FGFR1 amplification and hormone receptor (HR) status. FGFR1 amplification was assessed by silver in situ hybridization. Preplanned retrospective analyses assessed predictive value of FGFR1, FGFR2, and FGF3 amplifications by quantitative PCR (qPCR).

RESULTS

Dovitinib monotherapy inhibits proliferation in FGFR1- and FGFR2-amplified, but not FGFR-normal, breast cancer cell lines. Dovitinib also inhibits tumor growth in FGFR1-amplified breast cancer xenografts. Eighty-one patients were enrolled in the trial. Unconfirmed response or stable disease for more than 6 months was observed in 5 (25%) and 1 (3%) patient(s) with FGFR1-amplified/HR-positive and FGFR1-nonamplified/HR-positive breast cancer. When qPCR-identified amplifications in FGFR1, FGFR2, or FGF3 were grouped to define an FGF pathway-amplified breast cancer in HR-positive patients, the mean reduction in target lesions was 21.1% compared with a 12.0% increase in patients who did not present with FGF pathway-amplified breast cancer.

CONCLUSION

Dovitinib showed antitumor activity in FGFR-amplified breast cancer cell lines and may have activity in breast cancers with FGF pathway amplification.

A validated tumorgraft model reveals activity of dovitinib against renal cell carcinoma

Most anticancer drugs entering clinical trials fail to achieve approval from the U.S. Food and Drug Administration. Drug development is hampered by the lack of preclinical models with therapeutic predictive value. Herein, we report the development and validation of a tumorgraft model of renal cell carcinoma (RCC) and its application to the evaluation of an experimental drug. Tumor samples from 94 patients were implanted in the kidneys of mice without additives or disaggregation. Tumors from 35 of these patients formed tumorgrafts, and 16 stable lines were established. Samples from metastatic sites engrafted at higher frequency than those from primary tumors, and stable engraftment of primary tumors in mice correlated with decreased patient survival. Tumorgrafts retained the histology, gene expression, DNA copy number alterations, and more than 90% of the protein-coding gene mutations of the corresponding tumors. As determined by the induction of hypercalcemia in tumorgraft-bearing mice, tumorgrafts retained the ability to induce paraneoplastic syndromes. In studies simulating drug exposures in patients, RCC tumorgraft growth was inhibited by sunitinib and sirolimus (the active metabolite of temsirolimus in humans), but not by erlotinib, which was used as a control. Dovitinib, a drug in clinical development, showed greater activity than sunitinib and sirolimus. The routine incorporation of models recapitulating the molecular genetics and drug sensitivities of human tumors into preclinical programs has the potential to improve oncology drug development.

Fibroblast growth factor receptor-3 in urothelial tumorigenesis

Fibroblast growth factor receptor-3 (FGFR3) is a receptor tyrosine kinase implicated in the tumorigenesis of multiple malignancies, including bladder and other urothelial cancers, multiple myeloma, and cervical cancer. In urothelial carcinoma (UC), constitutive receptor activation occurs most commonly through substitution of a wild-type residue with cysteine in the extracellular domain of FGFR3, thereby resulting in dimerization (through disulfide bridge formation) and subsequent stimulation of tyrosine kinase activity. Activating mutations of FGFR3 have been observed in up to 70% of non-muscle-invasive bladder tumors, while overexpression of a wild-type receptor, found in approximately 40% of tumors, has been correlated with more invasive disease. The identification of FGFR3 mutations in UC has sparked substantial interest in the therapeutic exploitation of these aberrations, and in vitro studies have provided evidence that such alterations may represent driver oncogenic lesions. In this review, we discuss the biologic and prognostic impact of FGFR3 mutations in UC as well as FGFR3 as a potential target for novel therapeutics.

Phase I/II and pharmacodynamic study of dovitinib (TKI258), an inhibitor of fibroblast growth factor receptors and VEGF receptors, in patients with advanced melanoma

PURPOSE

Dovitinib (TKI258) is an orally available inhibitor of fibroblast growth factor (FGF), VEGF, and platelet-derived growth factor receptors. This phase I/II dose-escalation study was conducted to evaluate the safety, pharmacodynamics, and preliminary efficacy of dovitinib in the treatment of advanced melanoma.

EXPERIMENTAL DESIGN

Patients with advanced melanoma resistant or refractory to standard therapies or for whom no standard therapy was available were enrolled. Dovitinib was administered at doses ranging from 200 to 500 mg/d.

RESULTS

Forty-seven patients were enrolled. The most frequently reported adverse events were fatigue (77%; grade ≥3, 28%), diarrhea (77%; grade ≥3, 11%), and nausea (77%; grade ≥3, 9%). Six dose-limiting toxicities were observed in the 400-mg and 500-mg dose cohorts, which consisted of grade 3 nausea, fatigue, and diarrhea and grade 4 fatigue events. The maximum tolerated dose was 400 mg/d. The best tumor response was stable disease, which was observed in 12 patients. Increases in plasma FGF23, VEGF, and placental growth factor and decreases in soluble VEGF receptor 2 were noted during the first cycle of treatment, consistent with FGF receptor (FGFR) and VEGF receptor (VEGFR) inhibition. Dynamic contrast-enhanced MRI analysis showed a dose-dependent decrease in tumor blood flow and vascular permeability with dovitinib therapy. A decrease in FGFR phosphorylation was observed in paired tumor biopsy samples from a patient treated with dovitinib at a dose of 400 mg/d.

CONCLUSIONS

At a dose of 400 mg/d, dovitinib showed an acceptable safety profile and limited clinical benefit and inhibited FGFR and VEGFR.

New targeted therapies for renal cell carcinoma

INTRODUCTION

The aim of treatment in metastatic renal cell carcinoma is palliation. In the last 5 years, multiple targeted agents have been developed which have resulted in prolongation of patients' lives, but complete responses remain rare. New therapies and approaches are required to further improve the prognosis for patients with this disease.

AREAS COVERED

This review discusses the molecular targets in renal cell carcinoma relevant to the development of new treatments and describes the progress of novel therapies. The evidence is compiled from the PubMed database and proceedings of scientific meetings, searched up to December 2010.

EXPERT OPINION

A multitude of experimental agents are in clinical development and offer theoretical advantages over those currently in use. It is hoped that these treatments will result in better long-term control of metastatic renal cell carcinoma, with improved side effect profiles, but curative treatment in this disease remains elusive until the mechanisms underlying response and resistance to therapy are elucidated. Progress in the field has been limited by inadequate tissue collection within clinical trials; current and future clinical trial design will incorporate a larger translational component in an attempt to establish predictive biomarkers.

Perspectives in drug development for metastatic renal cell cancer

Patients with renal cell carcinoma (RCC) exhibit a spectrum of clinical outcomes, with some patients following an indolent clinical course and others displaying rapidly advancing disease. As evidence points to RCC being largely refractory to traditional chemotherapy and radiotherapy strategies, immunotherapeutic approaches played a dominant role in the management of metastatic RCC for a quarter of a century. Management of this challenging tumor has been revolutionized by the incorporation of molecularly targeted therapies such as inhibitors of pathways involving tyrosine kinase signaling and the mammalian target of rapamycin (mTOR). The improvements in disease stabilization and survival seen with these agents has meant that molecularly targeted therapy now forms the foundation for treating RCC and has resulted in a multitude of studies investigating similar compounds for efficacy in RCC. Despite this, the rationale for using immunomodulatory regimens remains strong and its ongoing place in this era of targeted treatments continues to pose interesting clinical questions. The challenge of maintaining durable responses from our current therapies persists and this review highlights the plethora of options now available in RCC treatment and the directions in which modern management are heading.